The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The further miniaturization of the various components, however, presents its own set of challenges and obstacles, microwave assisted magnetic recording (MAMR) techniques and shingled magnetic recording (SMR) techniques have been proposed as techniques for obtaining high recording densities. In order to reduce the bit size and to maintain thermal stability of the medium as the density increases, a medium using a material having high magnetic anisotropy is more useful. However, when recording on this type of medium, recording becomes difficult because of the reduction in the magnetic field when using a recording head that has a corresponding size (i.e., it is miniaturized). In a MAMR system, an alternating current (AC) magnetic field to the medium to reverse the magnetization even when the magnetic field from the recording head is insufficient to achieve a bit flip.
In a SMR system, the manufacturing yield of the recording head may be improved because a writing head having a wide width is used because overwrites occur when the track widths are narrow.
In MAMR, an AC magnetic field is generated by a spin-torque oscillator (STO), but to obtain a large assistance effect, the STO must be sufficiently small so that a single magnetic domain is formed during oscillation. According to some conventional heads, the performance of SMR system may be improved by offsetting the STO from the end of the writing head when MAMR is used in the SMR system, and by using a STO having a narrower width than the recording head.
On the other hand, in a hard disk drive (HDD), when a skew angle is given to the head, a magnetic field distribution corresponding to the shape of the air bearing surface of the writing head is generated, but the equi-magnetic potential lines of the recording magnetic field leak from the track, and the recording magnetic field leaks become noise. Therefore, both sides of the head are used differently in response to the skew angle so that there is no leakage from the track, and the characteristics do not degrade. It is important to maintain high performance characteristics on both sides of the head.
In addition, in a MAMR head, the efficiency of the assisted recording is improved by placing the STOs in the trailing gaps of the recording head. However, because of the difficulty in fabricating the STOs from thinner films, some problems occur when attempting to produce such as head, including narrowing the trailing gap, improving the magnetic field gradient of the recording head, and improving the recording performance. In one conventional head, asymmetric trailing gap lengths and a projection of a part of the main pole in the recording head has been used.